(1) Field of the Invention
The present invention relates to a synthetic resin molded article having a good and durable antistatic property and a process for the preparation thereof.
(2) Description of the Related Art
At the present, many synthetic resin molded articles having many good properties are marketed, but since they generally have a high electric resistance and are easily charged with electricity by friction or the like, they attract dust and dirt, and thus the appearance thereof becomes poor.
As the means for imparting an antistatic property to synthetic resin molded articles, there can be mentioned (1) internal addition of a surface active agent, (2) surface coating with a surface active agent, (3) surface coating with a silicon compound and (4) surface modification by a plasma treatment. Of these methods, methods (3) and (4) are not practical because of the high cost thereof, and methods (1) and (2) are generally adopted.
In the method of the internal addition of a surface active agent, since a surface active agent is incorporated or dispersed in a synthetic resin-forming starting material before the polymerization or a synthetic resin before the molding, the preparation steps can be simplified, but to obtain a required antistatic property, it is generally necessary to increase the amount of a surface active agent. This increase of the amount of the surface active agent added, however, tends to result in a lowering of the mechanical strength of the synthetic resin, and the obtained antistatic property is easily lost when washed with water or by rubbing.
The method of coating the surface with a surface active agent is advantageous in that the physical properties of the synthetic resin as the substrate are not lowered and a good antistatic property can be obtained with a small amount of the surface active agent. On the other hand, since the surface-coating step is necessary, an additional cost is required, and there is a danger that the beautiful appearance inherently possessed by a synthetic resin molded article will be lost. Moreover, the method has a problem in that the obtained antistatic property is easily lost by water washing or rubbing.
The inventors previously disclosed a cationic antistatic polymer having a quaternary ammonium base therein in Japanese Unexamined Patent Publication No. 63-108040, but this cationic polymer has a poor heat stability, and thus the polymer is adversely affected by heat.